As communication services and products continue to grow and expand, so does the need to enforce policy within a communication network. While applications such as push-to-talk, video-telephony, and enterprise video conferencing have enhanced communications, they necessitate a broader range of policy enforcement capabilities. In particular, because such applications may operate using Session Initiation Protocol (SIP), they require unique interfaces between network devices to enforce policy. Further complicating policy enforcement is the need to provide user-specific policies since every subscriber is not the same and some will pay more for their services than others. Enforcing a user-specific policy in a modern communications environment wherein a user may roam between networks hosted by different providers also presents a predicament as the user's policy profile is typically only stored by the home service provider.
The IP Multimedia Subsystem (IMS) is a next generation networking architecture that allows service providers to provide both mobile and fixed multimedia services. Because IMS runs over the Internet protocol (IP) it allows a service provider to provide any service which the Internet can or will support. While the IMS architecture has numerous benefits, it currently only supports SIP enabled devices. Accordingly, it is not able to provide roaming policy support for many legacy devices and applications that do not use SIP. Further, the range of policy control which the system provides is limited to Quality of Service (QoS) and accounting. Given the breadth of features and the range of network resources necessary to support such features, it is desirable to enable a broader range of policy control.